Norovirus is a genus of genetically diverse single-stranded RNA, non-enveloped viruses in the Caliciviridae family. The known viruses in the genus are all considered to be the strains of a single species called Norwalk virus. The viruses are transmitted by fecally contaminated food or water; by person-to-person contact; and via aerosolization of the virus and subsequent contamination of surfaces. Noroviruses are the most common cause of viral gastroenteritis in humans, and affect people of all ages.
Probiotic bacteria are known to stimulate the immune system and exert a competitive exclusion of pathogenic and putrefactive bacteria, reduce the amounts of ammonia and cholesterol in the blood, and promote absorption of minerals (50). Additionally, probiotic bacteria produce antagonist effects against pathogenic microorganisms; stimulate the immune system; improve lactose digestion; are lipolytic, thereby allowing fats to be more digestible; reduce plasma cholesterol; protect the intestinal mucosa, thereby assuring effective assimilation of the nutritive substances; produce polysaccharides that are active on some tumors; and reduce viability of some enzyme-producing microorganisms which catalyze the conversion of procarcinogenic substances into carcinogenic substances. It is believed that the probiotic bacteria exert their effects in a synergistic manner to curtail and retard the growth of pathogenic and detrimental bacteria of the gut (51 and 52).
It is believed that the health and well being of people and animals can be positively or negatively influenced by the microorganisms which inhabit the gastrointestinal tract, and in particular the large bowel. These microorganisms through the production of toxins, metabolic by-products, short chain fatty acids, and the like affect the physiological condition of the host and improve the physiological well being of the host. As a result, research has focused on using probiotic cultures in a variety of compositions and methods to improve health.
For example, US 20040161422 discloses a nutritional food product comprising at least one probiotic bacteria to improve gut function. U.S. 20040115177 discloses methods of administering probiotic bacteria to livestock animals in an amount effective to reduce the amount of hazardous bacteria. Dietary supplements such as those for example sold as part of the PARINAT™ line is formulated with Lactobacillus acidophilus strain L.B. and is stated to be beneficial for general digestive and intestinal problems.
US 20110262400 (incorporated herein by reference in its entirety) describes the use of certain secreted molecules isolated from probiotic bacteria for treating or preventing infection by harmful enteric pathogens in mammals, such as Escherichia coli O157:H7 and Salmonella. 
In view of the foregoing, it would be desirous to isolate and characterize the factor(s) produced by probiotic bacteria that provide beneficial effects in mammals for prophylaxis, prevention and treatment of harmful viral infection as well as use of such molecules as nutritional and food supplements for general health.